<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>绘制一个三角形</title>
    <style>
        .triagnle {
            width: 0;
            height: 0;
            border-left: 50px solid transparent;
            border-right: 50px solid transparent;
            border-bottom: 100px solid #000;
            outline: 1px solid skyblue;
            box-shadow: 0 0 10px #000;
        }
    </style>
</head>

<body>
    <div class="triagnle"></div>
</body>

</html>